Stretching of textile material



March 17, 1942. F. B.H1L| ETAL 2,275,394

SVTRETCHING OF TEXTILE MATERIALS Filed Dec. 2,8, 1940 Patented Mar. 17., 1942 sTnETcmNG or TEXTILE MATERIAL Frank Brentnall Hill, Maitland Walton Alford and Thomas Jackson, Spondon, near Derby, England, assignors to Celanese Corporation of America, a corporation of Delaware Appneatie neeember 2s, 1940, serial Ne. 372,108 In Great Britain January 12, 1940 10 lClaims.

This invention relates to improvements in or relating to the stretching of textile materials', and in particular to the operation-of stretching material in the form of filaments or threads by applying tension to said material while it is travelling, and is under the influence of a softening medium, for such purposes as increasing the strength of the material. Such operations are particularly applicable to the treatment of ma.

terials of cellulose acetate or other derivatives of cellulose. British Patents Nos. 438,584, 438,587, and U. S. Patents Nos. 2,142,909, 2,142,910 and 2,118,856 describe operations in which steam or hot water, or a liquid containing a solvent or softening agent is used as the softening medium for enabling the stretch to be imparted.

As applied to the stretching of material in the form of filaments or threads. an operation of the character in question isusually performed on a considerable number of ends, e.c g. of cellulose acetate or similar threads or filaments, and at the beginning of the operation the ends are drawn through the stretching apparatus and arranged in warp formation with suitable spacing between the threads. On the application of the softening medium, softening of the material of the threads takes place gradually and the threads can be drawn from the apparatus at a continuously increasing speed. It is necessary that the material be kept moving, since otherwise it would be unable to withstand the maintained action of the softening medium and breakages would result. Considerable skill and( practice is necessary to avoid frequent breakdowns and consequent wastage of materials. It is a primary object of the present invention to provide a method and means for facilitating the beginning of the stretching operation, the methody and means provided being capable, as a secondary function, of facilitating the termination of the operation without the unthreading of the ends from the stretching apparatus.

According to the present invention, in an operation for stretching material in the form of laments or threads by applying tension to said material while it is travelling and is under influence of a softening medium, the degree of stretch effect is changed, for starting the operation or for terminating it, by placing the output-input ratio of the material under the control of the tension in the material as it leaves the softening medium, and changing thev intensity of application of said softening medium, whereby said speed ratio is varied inversely with the variation in tension consequent on the varying softening influence of said softening medium. In this way, the degree of stretching of the material is made a function of the increasing softness of the material as the supply of softening medium is turned on during thestarting up of thev operation, sothat the necessary `raising of the degree of 'stretch until vthe required degree has been reached maybe made to follow automatically upon the softening in a smooth and rapid manner. In a similar manner, as the supply of softening medium is cut off at the end of the operation, the degree of stretch may be automatically reduced. For the purpose of controlling the output-input ratio in the desired manner, tension-sensitive means may be provided with which the material may be caused to pass in engagement, the movement of the tension-sensitive means being used to govern a speed regulator for a pulley or roller by which -the material is drawn through the stretching apparatus. Thus the material may be caused to pass over a spring-loaded pulley the movement of which, produced by the tension in the material I acting against the spring, is used for this purpose.

When a number of threads have passed through the softening medium in warp form, they may be gathered into a rope and passed in engagement with the pressure-sensitive means, e. g., over a pulley on a member movable. against the action of a spring, so that at the starting of the operation when the threads are capable of ex-v erting a higher tension, the member is swung in one direction and thereafter begins to move in the other direction as the softening weakens the threads and permits them to exert a lesser tension. Advantageously, the movable member may be used to guide the threads to a take-up or feed roller of conical or other form and to vary the point along the axis of the roller to which the threads are guided, so that the move- 'ment of the member carries the threads from a smaller diameter to a larger diameter as softening proceeds. Consequently, the increased softening of the threads is automatically accompanied by an increased rate of take-up, the

movable' member serving as a compensator throughout the initial stages of the operation.

For fully automatic working, the smalldiameter of the roller may .be such that the peripheral speed of that part of the roller equals the input speed of the threads to the stretching apparatus and the large diameter of the roller may be such that its peripheral speed equals the desired outputrate of the stretched threads. In

,other words, the ratio between the large and the small diameters of the roller equals the degree of stretch to be imparted, and the conical or other surface connecting the large and vsmall diameters provides or a progressive increase of the rate of stretching until the nal desired degree of stretch, e. g., 5, 10, 20 or more times is reached.

The threads may be delivered from the takeup or feed roller to any desired point, or the threads may be transferred from the roller to some other take-up device, the large part of the roller thus serving as a waste roller in the interval lapsing between the time full stretch has been reached and the time at whichallthe threads have been connected to their ultimate. take-up devices. When the threads have reached full strength, they may be disconnected from the compensator member.

By way of example one arrangement ofapparatus suitable for carrying out the invention will now be described in greater detail with reference to the accompanying drawing in which:

Fig. 1 is a part sectional diagrammatic side elevation of the apparatus and Y Fig. 2 is a plan view of the apparatus.

In the apparatus shown a number of threads I are taken from bobbins y2 mounted in a creel 3, are led through guide-eyes 4 in connection with the creel 3 and proceed from' the guideeyes 4 to a spacing comb 5. From the comb 5 the threads I enter a stretching apparatus of the general form described in U. S. Patent No. 2,142,909. This comprises an outer chamber 6 having apertures 'I through which the threads enter and containing nip-rollers 8 by means o! which the rate at which the threadsy are drawn into the stretching apparatus is accurately controlled. From the chamber 8 the threads pass to a stretching chamber 9, entering through apertures .I and leaving through apertures II. During the stretching operation the stretching chamber 9 is supplied through a pipe I2 with moist steam under pressure and the chamber 6 is supplied with compressed air through a pipe I3. The compressed air in the chamber 6 is' supplied at a pressure slightly lower than that of the steam in the chamber 9, and minimizes the ow of steam from the chamber 9 through the apertures I0, so that the threads, softened in the chamber 9 are not broken by being blown back into the chamber 5.

During the initiation of the stretching opera-4 tion, with which the present invention is specially concerned, the supply of both steam and air through the pipes I2 and I3 respectively is at first shut off, so that the threads I may be led through the chambers i and 9. The threads emerging from the apertures II are gathered as a rope, which passes round a xed guide pulley I4, round which it turns at an angle of approximately 90, and proceeds to a guide pulley I mounted on a vertical axis on a compensator bar I8 pivoted at I'I and carrying a further pulley l8 on`a horizontal axis at its other end. A

spiral spring I9 urges the compensator bar I9 in a counter-clockwise direction from above, and the pull of the threads I between the pulleys I4 and I5 initially counteracts the pressure of the spring I9. The compensator bar I5, with its pulleys I5 and I8 and spring I9 together constitute the tension-sensitive means of the apparatus. The pulley I8 guides the rope of threads I to a conical miler made up of three partsk 2|, 22 and 23, the parts 2| and 23 beingV cylindrical and having diameters proportional is avoided since any excessive tension placed l respectively to the unstretched length of the threads and the stretched length desired. The part 22 is-the conical part, and connects the parts 2| and 23. The length of the part 22 and the position of the point I1 are arranged so that the ,pulley I8 is always` close to one or other ol' the parts, 2|, 22, 23, and guides A. the threads I passing over it accurately to the conical roller, to the under side of which the threads pass.

Co-operating with the large part 23 of the conical roller is a further roller 24 constituting. with the roller 23 a pair of nip-rollers similar to the rollers 8 in the chamber 6. Beyond the rollers 23 and 24 there are a further comb 25, a set of three drying drums 28, a further comb 2l, a pair of mangle rollers 28 and the takeup creel for the collection of the stretched threads. The comb 2`I and the. mangle rollers 28 are wider than the nip rollers 8 and 24, being l the conical roller are then driven at such a speed that the peripheral speed of the nip-rollers 8 is equal to that ot the, small part 2| of the conical roller. At this stage the compensator bar I6 occupies the position shown in full in Figure 2 and is maintained in that position by the tens'ion in the threads'I between the pulleys I4 and I5. When the threads I are running through the apparatus, the steam is turned on through the pipe I2 and the compressedair through the pipe |3,so that the threads are softened in the chamber 9. As the threads I are softened in the chamber 9 they become unable to maintain their formertension between the pulleys I4 and I5, and in consequence the compensator bar pivots, under the action of the spiral spring I9, in an anti-clockwise direction, this movement ccntinuingas the softness of the threads increases. As a result of this the pulley IB guides the threads I up the conical part 22 of the conical roller and this causes the softened threads to be stretched. Excessive stretching of the threads upon them would act between the pulleys I4 and I5 and prevent further pivoting of the compensator bar I6. In this way the threads automatlcally receive as much stretch as the softening effected in the chamber 9 enables them to undergo without breaking. As the steam pressure builds up in the chamber 9 the threads become suillciently softened for the. pulley I8 to guide them on the large part 23 of the conical roller. When this occurs the desired degree of stretch has been reached, and the threads may be slipped off the pulleys I 4,- I5 and I8 and proceed direct from the apertures II to the roller 23.

During the operations described above,l the threads I have been collecting asA waste on the free parts 2|, 22 and 23 of the conicall roller. As soon as the threads are disengaged from the pulleys I4, I5 and I8, however, the rope of threads iscut on the upper part of the roller 23, at the point where they haveupass'ed about half way round the roller. Thescut end of the rope is then led quickly over the roller 24, over the comb 25, round the dryingdrums 26, over the comb 21, through the mangle rollers 28 and atraen I on to a waste swift 2l forming part of the takeup creel. The threads in vthe rope are .then separated into the dents of the comb 2l so that they run as a sheet, indicated at Si, under and. over the nip-rolls 23,14' and round the drying drums 26. The threads maythen be taken one by one, dropped into the appropriate dents of the reed 2l, detached from the swift 28 and led to the separate take-up bobbins, indicated Adiagrammatically at 3l, of the take-up creel.

`trol the speed of the threads after they have passed round the drying drums 2l. The taire-up packages 3l are arranged to rotatev at an appro-v x3 threads by' applying tension to said material'v while it is travelling and issunderethaingulce of a softening medium, Saldi method comprisin drawing the material under tension out of the softening medium during the initial application thereof to the material, and employing the tension in the material as it leaves said softening medium to control the 'rate of said drawing and tc increase said rate up to a desired limit as the hanced due to the increasing softeninginfluence priate speed to collect the stretched" threads as fast as they are delivered.

When it is desiredto terminate the operation, e. g. on approaching exhaustion of the supply packages 2, the threads I are connected again as a rope which is slipped on the pulleys I6, i5 and I8, and are severed beyond the nip rollers 23,24, so that they collect as waste on the lower roller 2t. The steam supply is then turned off, and as the softness of the threads I decreases in consequence, the increasing tension in the threads rotates the compensator bar I6 till the threads are guided to the small end 2l of the conical roller. vThe rollers 2l and S may then be stopped, leaving the threads i threaded through the chambers t and t ready for restarting. If the supply is to be replenished by replacing the bobbins 2, the new ends have merely to be tied in to the old ends, and do not need to be threaded through the chamber and 8.

'While a conical surface is a convenient formfor the portion is of the roller connecting the small and large parts 2| and 23, other forms of surface Imay be employed, for example concave or convex or concavo-convex. In general, the precise form of the surface 22 is immaterial, sine/e .the surface has merely yto provide the possibility of an increasing rate of stretch without, however, controlling the precise amount of stretch that will be imparted at any given interval after the threads begin to soften. The degree of stretching during the starting operation is governed by the ability of the threads themselves to receive stretch, since the weakening of the threads accompanying the softening governs the position of the compensator bar. Consequently the invention enables starting up to be readily accomplished with yarns of different characteristics and provides automatic compensation whatever the degree of stretchthat is to be imparted.

Having described our invention, what we desire to secure by Letters Patent is:

l. In an operation for stretching material in the form of filaments or threads by applying tension to said material while it is travelling and is under the lnuence of a-softening medium, the steps of changing the degree of stretch effected by placing the output-input speed ratio of the material under the control of the tension in the material as it leaves the softening medium, said speed ratio being lvaried in accordance with the extent of the softening of the material due to the softening inuence of said softening mediunn;v y

2. Method` of,;"starting. up -an operation for stretching ma erialintheform of filaments or extent of the softening vof the material is enof said medium during )its initial application.

3. Method of terminating an operation for stretching material in the form of laments or threads by applying tension to said material while it is travelling and is under the vinfluence of a softening medium, said method comprisingv placing the speed at which the material leaves the softening medium under the control of thev 'tension in .the material as it leaves said softening medium and cutting off the supply of softening medium to the materiaLvwhereby said speed is diminished as the extent of the softening of the material is lessened due to the decrease softening influence of said medium as its supply is cut o.

4. Method of starting up an operation for stretching material in the form of filaments or threads by applying tension to said material while itis travelling and is under the influence of a softeningA medium, said method comprising guiding the material to a conical member is guided and to carry the material towards the larger end of said conical member as the material is softened by said softening medium during its initial application.

5. Method of terminating an operation for stretching material in the form of filaments or threads by applying tension to said material while it is travelling and is under the influence of a' softening medium, said method comprising placing the material under the control of a conical member to which the material is guided as it leaves the softening medium and controlling .the point along the axis of said conical member to which said material is guided in accordance with the tension of the material and cutting o the supply of the softening medium to the material whereby the material is carried towards the smaller end of said conical member as the extent of the softening of the material is lessened due to the decreasing softening influence of said medium as its supply is cut off.

6. Method of starting up an operation for stretching material in the form of filaments or threads by applying tension to said material while it is travelling through and is under the influence of a softening medium, said method comprising drawing the material under tension out of the softening medium during the initial application thereof to the material, and employing the tension in the material as it leaves said softening medium to control the rate of said drawing and to increase said rate from one substantially equal to the speed at which the-material is fed into the softening medium up to a desired limit as the extent of the softening of the material is enhanced due to the increasing softening influence of said medium during its initial application.

'1. Method of terminating an operation for stretching material in the form of illaments or threads by applying tension to said material while it is travelling through and is under the inuence of a softening medium, said method comprising placing the speed at which the material leaves the softening medium under the control of the tension in the material as it leaves said softening medium and cutting off the supply of softening medium to the material, whereby as the extent of the softening of the material is lessened due to the decreasing softening influence of said medium as its supply is cut off, said speed is diminished to one substantially equal to the speed at which the material is fed into the softening medium.

8. In apparatus for stretching material in the form of filaments or threads, the combination with a chamber for the application of softening medium to the material while it is travelling,

means for positively feeding the materialinto said chamber and means for positively drawing the material out of said chamber, of tension-sensitive means adapted to engage the material as it leaves said chamber, said tension-sensitive means being adapted to vary the output-input ratio of said feed and drawing means.

9. In apparatus for stretching material in the form of filaments or threads, the combination with achamber for the application of softening medium to the material while it is travelling, means for positively feeding the material into said chamber and a conical roller for positively drawing the material out of said chamber, of tenl0. In apparatus for stretching material in the I form of laments or threads, the combination with a chamber for the application -of softening medium to the material while it is travelling, means for positively .feeding the material into said chamber and a conical roller for positively drawing the material out of said chamber, of a spring-loaded lever between said feeding and drawing means and guide means at one end of said lever adapted to engage the material as -it leaves said chamber and to deflect the material through an angle whereby the tension of said material, acting against the loading of said lever, controls the position of said lever so as to vary the point along the axis of'said roller to which the material is guided and thus to vary the output-input ratio of said conical roller and said feeding means.

FRANK BRENTNALL HILL. MAITLAND WALTON ALFORD. THOMAS JACKSON. 

